Want to Talk to Your Mac’s Serial Port?  Check Out CoolTerm!

| Monday's Mac Gadget

Product Link : CoolTerm (Freeware/Donationware)

Before there was USB (Universal Serial Bus) many computers, be they from Apple or another vendor, used a serial port to connect to various devices, such as modems and printers. The most common flavors of serial port were RS-232, with Apple implementing a more robust standard known as RS-422. Sadly, Mac OS X doesn't include a decent terminal program that can talk to serial ports. Enter CoolTerm.

Once you start CoolTerm, the first thing you'll want to do is select Options, which will let you select your serial port, as well as the baud rate (speed) and number of data bits, parity and stop bits. These are often represented in a shorthand such as 81N (8 data bits, 1 stop bit, no parity) or 71E (7 data bits, 1 stop bit, even parity) by the maker of the serial device. Make sure you get all of these exactly right, or you'll see meaningless garbage on your screen. You can also set the method of flow control, which is how the serial port tell the device to stop sending data if it is coming in too fast. This can be done via hardware signals (CTS or DTR) or software (XON).

CoolTerm Talking to a Bluetooth Cellphone

Once you've configured the parameters, click on the Connect button. If everything is set up correctly, you'll see the name of the serial port, the speed and data word format, and the word Connected on the bottom of your screen.  You'll also be shown the state of the various control signals, including RTS, DTR, DCD, CTS, DSR and RI. You can then start typing in real time, or use the Send String feature to enter an ASCII or Hex string and send it all at once. There are some other handy options, such as an option to view the Hex values of the data. You can also capture your session to a file for later analysis.

Wait, you are saying, I don't have any serial ports on my Mac! Well, you probably do, but don't know it. If you have a modem, you'll have a serial port called Modem, and if you have Bluetooth, the you have a serial port called Bluetooth-Modem, which is used if you tether your cellphone to your Mac. The above screenshot shows some of the information your cellphone will provide if you issue an "ATI" command.

So start talking to your serial devices, and try CoolTerm today! Have any other programs that let you interact with your devices? Send an email to John and he'll check it out.

Comments

Mike Weasner

Sounds a like a great tool for troubleshooting serial connections made via a USB-serial adapter.  I’ll mention it on my ETX Site for testing telescope handcontroller connections from Mac OS X.  Thanks to you for mentioning it and to the developer for writing it.

John F. Braun

Sounds a like a great tool for troubleshooting serial connections made via a USB-serial adapter.? I?ll mention it on my ETX Site for testing telescope handcontroller connections from Mac OS X.? Thanks to you for mentioning it and to the developer for writing it.

I’ve found reports that an old favorite, ZTerm, has issues with some USB to serial adapters under Snow Leopard, which makes this a worth alternative.

jbruni

You can simply use Terminal to talk to your modem. Connect to the device using the screen command:

screen /dev/cu.Bluetooth-Modem 

Replace “/dev/cu.Bluetooth-Modem” with whatever your device is named. You can fiddle with line controls using the “stty” command.

Chris R

Cornflake is another great serial terminal for Mac OS X.  You can download it at http://tomgerhardt.com/Cornflake/

Gus S. Calabrese

Another fairly simple approach is to buy RealBasic for OS X.  The single user price is $99.  It has great support for serial ports.  It has an example of a how to build a serial terminal emulator.  The best part is that you can really customize / automate how your serial connections work.

Roger Meier

Another fairly simple approach is to buy RealBasic for OS X.  The single user price is $99.  It has great support for serial ports.  It has an example of a how to build a serial terminal emulator.  The best part is that you can really customize / automate how your serial connections work.

As a matter of fact, CoolTerm was written in REALBasic. I.e. CoolTerm is a good example of what REALBasic is capable of.

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